1. Field of the Invention
The present invention relates generally to a pivotal micromotion device, and more specifically to a device used as means for finely adjusting pivotal motion with an ultrahigh accuracy in measuring instruments, machine tools, automated equipment, etc. for inspecting or manufacturing LSIs (large-scale integration circuits), for instance.
2. Description of the Prior Art
An example of the pivotal micromotion device as described above is introduced in NIKKEI MECHANICAL, 27th, Feb. 1984, page 86, FIG. 1.
This device is provided with a threaded rod driven by a pulse motor (or a step motor) and a movable body such as a nut engaged with the threaded rod and slightly movable along the longitudinal direction of the threaded rod without rotation. When this threaded rod is driven by the pulse motor, the movable body moves along the threaded rod. This straight motion or travel provides an external force to a pivotal body pivotably supported, through an appropriate transmission member such as a link, in the tangential direction of the pivotal body. Therefore, the pivotal body is pivoted a microscopic angle corresponding to the rotational angle of the threaded rod.
In the prior-art device as described above, in order to enhance the resolving power or the resolution in the pivoted angular displacement of the pivotal body, it is absolutely necessary to reduce the pitch of the threaded rod or the step angle of the pulse motor. However, there exists a machinability limit in reducing the pitch of the threaded rod, and the pulse motor becomes great in size and weight in reducing the step angle thereof, making it impossible to realize a compact pivotal micromotion device.